I shall threw my two pence worth...
Merge in turn signs are commonly used on both, permanent and temporary set ups.
In principle, they work quite well.
However, I don't feel there is an issue with signs and what specific information should they display, or not display. The problem lies with individuals, their level of traffic awareness, their driving aptitude, as well as attitude towards fellow drivers.
Have you ever wondered, why at some point you are doing 70mph on a motorway, only to be brought to a complete stop, then crawl at 10mph, through 30mph and back to 70?
In 9 out of 10 cases, this a result of tailgating, a vehicle cutting up another vehicle or similar, unsocial behaviour.
When you brake, so does the car behind you, so does the car behind him and so on. But at some point, way back from the initial vehicle braking another vehicle is brought to complete halt. In practice, few seconds of braking, can actually result in major congestion in that lane, that takes some time to clear up.
Very similar will apply to merging in turn situations. I will use A1m, junction 6 heading north as an example, which some of you will know very well.
Three lanes on the approach, where lane 3 merges with lane 2.
Now, strictly speaking there is nothing wrong with anybody driving as far as P1014 (directional arrow painted on the tarmac) and merge in turn with lane 2.
However, have you noticed that lane 1 always moves much, much quicker than lane 2 and lane 3? You might say, it is simply because lane 2 and 3 merge together, hence bear larger capacity in term of traffic flows.
Well, sorry to disappoint, but no. As a matter of fact, lane 1 has got higher traffic count per minute, than lane 2 and 3 combined.
How is that possible?
If you were to actually watch the traffic at this section of the road from bird view, ideally from CCTV camera located near by, you will see that lane 1 isn't actually carrying the traffic from lane 1 only. Most of local, regular drivers know that they will get quicker through the bottle neck in lane 1 than drivers in lane 2 and/or 3. This means huge number of drivers move over to lane 1 well before the merge in turn section.
And this is the key as to why lane 1 moves a lot quicker. Number of drivers, constantly move over from lane 2 to lane 1, but because it is done in good time, before cut off point, this keeps this lane moving. Yes it is slow pace, but moving nevertheless.
In the meantime, traffic in the lane 2 and lane 3 meet at a particular point where simply, someone has to give in. Problem is, a lot of a time nobody wants to. At this point, traffic is no longer flowing smoothly, it is more of a jerking movement as nobody wants to be mug and give way.
You may be aware that this specific junction is a subject to a major scheme next year. Lane 1 will become a dedicated filter lane coming off completely at junction 6. From that point there will only be two lanes running on the main carriageway.
What this will actually do, is force drivers into correct lane in a timely manner, oppose to uncontrolled cutting in at the very last moment. Of course there will be people driving down lane 1 and changing in the lane 2 at the very last point. But the idea is, that once people get used to the new layout, the traffic flows will improve over time.
In summary, you are not braking the law by driving in the closed lane to the very point of that lane being closed. But by doing so you actually contributing to congestion build up, or worse, putting lives at risk if that closed lane happen to have people working in there.
